Method and assembly for the production of a homogenous composite pipe of unspecified length

ABSTRACT

A method of forming a homogenous composite pipe of unspecified length from strips of fiber reinforced thermoplastic material is disclosed. A mandrel is arranged stationary in a process direction to extend freely from a first supported end to a second end. A slip-sheath is applied about the mandrel. The thermoplastic material strips are wound about the slip-sheath. A section of the thermoplastic material strip winding is consolidated. The slip-sheath is formed from tape material which is applied longitudinally onto the mandrel surface. The slip-sheath is connected to a puller arranged downstream of the mandrel in the process direction. Consolidated pipe sections are pulled off from the second end of the mandrel in synchronization with the winding and consolidation. An assembly for carrying out the method.

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a method for producing a pipe composedof strips of fibre reinforced thermoplastic that are wrapped about amandrel, whereupon heat is supplied for consolidation of the fibrereinforced thermoplastic to produce a composite pipe of unspecifiedlength. The present invention also relates to an assembly for producingsuch composite pipe of unspecified length.

The composite pipe in question finds use within different fields ofindustry where fluids need transporting, and is characterized throughlow weight, high strength and high chemical resistance. Advantageously,though not exclusively, the composite pipes may be employed as flexiblerisers, flow-lines, pipe-lines, umbilical pipes, pressure casings forprocess equipment, containers and structural members within the oil andgas industry.

Composite pipes of the type referred to are known to be produced bywinding and consolidating a strip- or band-shaped, fibre reinforcedthermoplastic, known as a prepreg, about a tubular base thatconventionally remains inside the consolidated thermoplastic, thusforming an internal liner which is bonded to the external pipe wall madeof cured thermoplastic material. The term “prepreg” refers to a mat,fabric, non-woven material or roving pre-impregnated with resin. Thefibre reinforced thermoplastic recited above is a polymer compositewhich is partially cured and ready for moulding, comprising fibresembedded in a matrix of thermoplastic polymer material which solidifiesinto the shape applied when cooled from a temperature effective formelting of the matrix. The solidifying process is called consolidation.The fibres may extend in essentially the one and same direction in aunidirectional manner.

Among the prior art available, reference can be made to WO 05/108046 A1,as well as WO 03/037770, each of which represents the prior art whichincludes the composites pipes having internal liners.

Likewise, JP-1198343 discloses a method by which a layer of prepregmaterial is wound onto a base layer comprising a carbon paper which ispreviously wound about a mandrel. The paper base and prepreg layers arebaked together, whereupon the mandrel is pulled out from the resultingbaked body. Pipes of specified lengths adapted to the length of themandrel are produced this way, and released by pulling the mandrel outfrom the resulting pipe.

Composite pipes having an internal liner bonded to external structurallayers made of thermoplastic materials may suffer the occurrence ofcracks and separation between the internal liner and the exteriorthermoplastic layer. One plausible cause for such separation and cracksformation is the use of different materials having different materialproperties for structuring the liner and thermoplastic external layer,respectively. The conditions under which the composite pipe operates maycontain temperature differentials over the pipe wall in the order ofseveral hundred degrees C, pipes combined in lengths that coverkilometre distances, transversal movements and bending causingcontra-directional axial loads on the pipe layers, high pressuresprevailing at substantial sea depths, etc.

An object of the present invention is thus to reduce or essentiallyeliminate the drawbacks related to the pipes structured through thecombination of an internal liner which is bonded to an external pipewall.

Another object is to provide a method and assembly through whichhomogenous composite pipes of unspecified lengths, or endless pipes, areproducible.

These objects are met in a composite pipe as produced through the methodof appended claims.

The objects are likewise met in a composite pipe as produced through theclaimed assembly for carrying out the method.

SUMMARY OF THE INVENTION

Briefly, in the present invention there is provided a production methodand an assembly by which multiple layers of fibre reinforcedthermoplastic strips are applied onto a mandrel to fabricate ahomogenous composite pipe of unspecified length.

The method of the present invention comprises the steps of: arranging amandrel stationary in a process direction to extend freely from a firstsupported end to a second end; applying a slip-sheath about the mandrel;winding the thermoplastic material strips about the slip-sheath; andconsolidation of a section of the thermoplastic material strip winding.The method is further characterized through the steps of

forming the slip-sheath from tape material which is appliedlongitudinally onto the mandrel surface;

connecting the slip-sheath to a pulling means arranged downstream of themandrel in the process direction, and

pulling consolidated pipe sections off from the second end of themandrel in synchronization with the steps of winding and consolidation.

The steps of winding and consolidation may be synchronized with anincremental pulling of consolidated sections of composite from themandrel, or may alternatively be synchronized with a continuous pullingof consolidated sections of composite from the mandrel.

Preferably, the slip-sheath material is a liquid-soluble material tape,and most preferred a cellulose fibre in a matrix of water-based resinformed into a tape, which is applied about the mandrel in advance of thewinding of strips of fibre reinforced thermoplastic, as seen in theprocess direction.

Advantageously, the winding is performed from singular or multiplesupplies of fibre reinforced thermoplastic driven through a revolvingpath about the mandrel.

The revolving supplies of fibre reinforced thermoplastic may be arrangedfor a reciprocating motion in the process direction, or mayalternatively and preferred be stationary arranged, with respect to theprocess direction.

Consolidation of the fibre reinforced thermoplastic is performed throughthe supply of heat to the wound strips of fibre reinforced thermoplasticat a location upstream of the second end of the mandrel. A heater with acapacity to apply, circumferentially, a temperature necessary formelting the polymer matrix of the fibre reinforced thermoplastic, may bearranged for reciprocating motion in the process direction, thoughalternatively and preferred the heater is stationary with respect to theprocess direction.

Pulling the homogenous composite pipe off from the second end of themandrel comprises further winding of consolidated pipe sections onto alarge diameter spool.

In the method, a finishing step comprises cleaning the pipe interiorfrom residues of slip-sheath material. The cleaning step may involveflooding the pipe interior with water, and/or mechanically removingresidues of slip-sheath material from the pipe interior.

An assembly by which a homogenous composite pipe of unspecified lengthis produced according to the method briefly comprises a mandrel which isstationary supported in a first end to extend freely in a processdirection from said first end to a second end; means for forming aslip-sheath about the mandrel; a winder mechanism revolving about themandrel downstream of said first end carrying at least one supply ofthermoplastic material strips; and a heater surrounding the mandrelupstream of said second end. The assembly is further characterized inthat said means for forming the slip-sheath about the mandrel isarranged to apply a tape material longitudinally onto the mandrelsurface, and in that a pulling means is arranged downstream of themandrel to be connectable to the slip-sheath.

The operations of the winder mechanism and heater are synchronized withan incremental operation of the pulling means. Alternatively andpreferred, the operations of the winder mechanism and heater aresynchronized with a continuous operation of the pulling means.

In a preferred embodiment, the slip-sheath applying means comprises atleast one rotary supply of tape-shaped slip-sheath material arrangedupstream of the winding mechanism for feeding the tape longitudinallyalong the mandrel. The slip-sheath applying means advantageouslycomprises a tape guide funnel arranged for forming the tapecircumferentially about the mandrel.

Advantageously, the pulling means comprises a large diameter spooldriven for rotation, onto which the composite pipe sections is woundfrom the mandrel.

Advantageously, the method and assembly of the present invention areimplemented in the production of a homogenous composite pipe suitable asa flow-line for transportation of fluids, such as oil and/or gas.

The method and assembly of the present invention are likewiseadvantageously implemented in the production of a homogenous compositepipe suitable as a sub-sea structure for the off-shore industry.

The method and assembly of the present invention are also advantageouslyimplemented in the production of a homogenous composite pipe suitable asa production or injection riser for oil and/or gas and/or water.

The method and assembly of the present invention are likewiseadvantageously implemented in the production of a homogenous compositepipe suitable as an umbilical pipe.

The invention thus makes fabrication of unspecified or continuouslengths of homogenous composite pipes possible, without relying on atubular member remaining inside the finished pipe as an internal liner.

The present invention provides an advantage above the prior art in thathomogenous pipe sections of unspecified length are producible in acontinuous manner, in other words endless pipes may be produced. Incontrast to a helically applied base layer, such as the one disclosed inJP-1198343, a slip-sheath applied in longitudinal direction onto themandrel surface as disclosed in the present invention provides reducedfrictional resistance as consolidated pipe sections are successivelypulled off from the stationary mandrel. By building the slip-sheath fromtapes extending in longitudinal direction, and connecting a pullingmeans to the slip-sheath, the pulling force applied is fully absorbed bythe slip-sheath and the helical windings of thermoplastic strips remainunaffected from any tensile stresses that would otherwise be appliedfrom the pulling means. This aspect is considered to be of importance inthe continuous production of pipes of unspecified lengths, whereinunconsolidated sections of helically wound thermoplastic strips aremoving along the mandrel as consolidated sections of the pipe are pulledoff from the mandrel.

The present invention is more closely explained below, with referencemade to the accompanying drawing.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

In the following, the expression “fibre reinforced thermoplastic” refersto a fibre reinforced polymer matrix, which cures into a solid statethrough a consolidation process where heat is applied to raise thetemperature of the polymer matrix above its melting point, followed bycooling. The expression “strips” shall be understood to comprise fibrereinforced thermoplastic shaped into bands or strings of suitable widthand thickness. The fibre may be a carbon fibre, Kevlar fibre, aramidfibre or glass fibre, or any suitable type of fibre. The fibres areembedded in a polymer matrix, such as high density polyethylene,cross-linked polyethylene, polyamide polyvinylidene fluoride, e.g, orany other polymer suitable for thermoforming. The fibres may be embeddedin the polymer matrix in the form of woven fabrics, roving, tows, oryarns, e.g. The strips of fibre reinforced thermoplastic preferablycontain fibres that are uni-directionally embedded in the polymermatrix. The fibre reinforced thermoplastic may have a fibre content of30-80% fibres per volume, and a strip thickness of typically about0.1-0.5 mm. The width transverse to the longitudinal direction of thestrips of fibre reinforced thermoplastic is typically about 1-25 mm.However, other widths, thicknesses, fibre contents, fibre and polymermaterials not mentioned may be applied in a fibre reinforcedthermoplastic which operates with the method and assembly of the presentinvention.

A “mandrel” as this term is used herein refers to a core utilized in athermoforming process as an element onto which a thermoplastic materialis shaped through the application of heat, and which is successivelyreleased from the produced composite pipe as the thermoplastic materialis solidified into the applied shape. A “liner” is a tubular elementonto which the thermoplastic material is shaped through the applicationof heat, and which remains included in the resulting composite pipe wallas the thermoplastic material consolidates onto the surface of theliner.

“Unspecified length” as used herein reflects the production ofcontinuous or endless pipe lengths, in contrast to pipe lengths adaptedto the length of a mandrel on which the pipes are formed.

The scope of invention also includes the application of fibre reinforcedthermosetting matrices in the composite wall structure, if appropriate.

An assembly for carrying out the method is diagrammatically illustratedin the drawing. With reference to the drawing, a mandrel 1 is stationarysupported in a first end 2 to extend freely in a process direction Pfrom a mandrel support 3, resting on a production plant floor, to asecond end 4. The second end 4 preferably is non-supported, however aroller support or similar (not illustrated) may be arranged below themandrel and the produced composite pipe in the region of the second end,if appropriate. The mandrel 1 provides the core in the process ofthermoforming a homogenous composite pipe having no internal liner. Themandrel 1, the diameter and cross-sectional shape of which determinesthe size and shape of the pipe, has a smooth outer surface and may beproduced of metal, preferably of steel, or any suitable syntheticsmaterial. The mandrel 1 may alternatively be produced from syntheticsmaterial and metal in combination, having for example an upstreamportion made of low friction synthetics material, and a downstreamportion with excellent stability against heat expansion in theconsolidation area, made of steel, e.g. The mandrel 1 typically has acircular section, and may be hollow.

At least one supply of thermoplastic strips 5 is carried in a windingmechanism 6 arranged and driven for revolving motion about the mandrel1, downstream of the mandrel support 3 as viewed in the processdirection P. The structure of a winding mechanism 6 typically comprisesa ring member rotationally journalled in a base member, as well as adrive means for revolving the ring onto which one or several supplies offibre reinforced thermoplastic strips are carried on rotary spools.Preferably, at least two supplies of fibre reinforced thermoplasticstrips are carried by the winding mechanism, which may be operated forwinding the strips 5 in helical paths about the mandrel 1, and with aback-tension that tightens the windings about the mandrel. Naturally,two or more winding mechanisms 6 may be arranged in succession along theprocess path.

Downstream of the winding mechanism 6, a heater 7 is arranged to supplyheat circumferentially about the wound strips of fibre reinforcedthermoplastic. The heater 7 is effective for raising the temperature inthe wound strips 5 sufficiently to reach the melt point temperature ofthe polymer matrix. Any suitable heating source known in the art isavailable for a heater 7, such as electromagnetic radiation, infraredradiation, laser radiation, microwave radiation, or hot gases, openflames, contact heat or vibration, e.g. by means of ultra sound, orelectrical resistance, or through any suitable combination thereof.

The heater 7 is positioned upstream of the second end 4 of the mandrelat a distance there from sufficient to ensure sufficient cooling andconsolidation of the composite pipe downstream of the heater, beforereleasing from the mandrel as will be explained below. If appropriate, acooler (not illustrated) may be arranged downstream of the heater 7.

In the heater, sufficient consolidation pressure is provided through aback-tension applied upon winding and maintained in the strips woundabout the mandrel, assisted from an anisotropic thermal expansion of thefibre reinforced thermoplastic strips typically having a thermalexpansion coefficient in the thickness direction which is considerablylarger than the same in a longitudinal direction of the strips.

A pulling means, in the drawing represented by a pulling line 8, issuccessively arranged in the process direction P and effective forpulling consolidated sections 9 of the resulting pipe off from thesecond end 4 of the mandrel. The pulling means may be realized as alarge diameter spool or carousel which is driven for rotation, known perse by the skilled person, and onto which the consolidated pipe issuccessively pulled off from the mandrel. Other suitable arrangementsfor the transport of a continuous pipe may be used as alternative to thementioned spool or carousel, as long as measures are provided forconnecting the pulling means to a longitudinally applied slip-sheath asexplained hereinafter.

According to the invention, the strips of fibre reinforced thermoplasticare wound onto a slip-sheath applied about the mandrel 1, under thewound layer/layers of fibre reinforced thermoplastic strips 5. Theslip-sheath is preferably made of a liquid-soluble material, which isformed into the shape of a band or tape. The slip-sheath material ischosen to withstand the melting temperature of the polymer matrix,reaching temperatures of about 300 degrees C., e.g., or more. Theslip-sheath may be a tape 10 containing organic fibres in a water-basedmatrix, such as a paper tape containing cellulose fibres, which iseffective for preventing the consolidated composite pipe from bondingonto the mandrel 1.

The tape 10 which is used for forming the slip-sheath is appliedlongitudinally to the mandrel surface. A supply 11 of tape 10 isarranged in the process direction upstream of the winding mechanism 6.As illustrated, two continuous lengths of tape 10 may be applied ontothe mandrel surface from diametrically opposite sides of the mandrel.The tapes 10 have a width sufficient to enclose the mandrelcircumferentially when applied in combination, and curved over themandrel surface. On application, the tapes 10 are introduced into a tapeguide funnel 12 arranged about the mandrel downstream of the tape supply11. The tape guide funnel 12 thus controls the tapes to conform to theshape of the mandrel, tightly following the typically circular surfaceof the mandrel.

Operation of the assembly is initiated through the application of theslip-sheath in longitudinal strips about the mandrel. Typically, twostrips of slip-sheath forming tapes 10 are fed from supplies 11 throughthe tape guide funnel 12 and past the fibre reinforced thermoplasticstrip winding mechanism 6. The ends of the tapes are then connected tothe pulling means, such as to the end of pulling line 8. Connecting tothe pulling line may be achieved in any suitable manner, such as througha connecting plug in the end of the pulling line onto which the tapeends of the slip-sheath are mechanically connected or bonded by means ofan adhesive, e.g. Winding of thermoplastic strips 5 about thetape-covered mandrel 1 is then synchronized with the operation of thepulling means, incrementally or continuously as preferred. Upon passagethrough the heater 7, or upon a halt therein, a section of the fibrereinforced thermoplastic strip winding is subjected to a temperaturenecessary for melting the polymer matrix. On exit from the heater thefibre reinforced thermoplastic strips consolidate into homogenouscomposite pipe sections which are successively pulled off from thesecond end of the mandrel 1, incrementally or continuously as preferred,by operation of the pulling means.

In a closing step of the method according to the present invention, thecomposite pipe is cleaned internally from the slip-sheath tape 10. Anyresidues of slip-sheath material may be removed by flooding the pipeinterior with a liquid, preferably water which is effective for removinga paper based slip-sheath material such as paper. Alternatively or inaddition thereto, a mechanical cleaning may be carried out by means ofrotating brushes which are driven or fed through the pipe interior, e.g.

Through the method and assembly disclosed herein, unspecified orcontinuous lengths of homogenously structured composites pipes may beproduced, lacking an internal liner. Due to the strength and inherentelasticity of the composite material, kilometre lengths may be producedthis way for industrial fluid transport, such as flow-lines, pipelines,sub-sea risers for oil and/or gas, umbilical pipes, etc., as well asstructural elements in off-shore and land-based applications.

The present invention provides an advantage above the prior compositepipes which include an internal liner, in that the entire pipe sectionis built up according to the invention as a homogenous material, andthus cracking due to different material properties can be avoided. Inaddition thereto, the suggested composite pipe and process iscost-saving, avoiding a separate process of fabricating an internalliner.

Modifications to the detailed design are possible within the scope ofinvention as defined through the appended claims. Thus, it will beappreciated by a man skilled in the art, that each feature disclosed insubordinated claims will contribute to the advantages of the inventionalso in other combinations than those expressively outlined in thesubordinated claims.

1. A method of forming a homogenous composite pipe of unspecified lengthfrom strips of fibre reinforced thermoplastic material, the methodcomprising: arranging a mandrel stationary in a process direction, toextend freely from a first supported end to a second end; applying aslip-sheath about the mandrel; winding the thermoplastic material stripsabout the slip-sheath; consolidating of a section of the thermoplasticmaterial strip winding: forming the slip-sheath from tape material whichis applied longitudinally onto the mandrel surface; connecting theslip-sheath to a pulling means arranged downstream of the mandrel in theprocess direction; and pulling consolidated pipe sections off from thesecond end of the mandrel in synchronization with the steps of windingand consolidation.
 2. The method according to claim 1, wherein thewinding and consolidation are synchronized with an incremental pullingof consolidated sections of fibre reinforced thermoplastic off from themandrel.
 3. The method of according to claim 1, wherein the winding andconsolidation are synchronized with a continuous pulling of consolidatedsections of fibre reinforced thermoplastic off from the mandrel.
 4. Themethod according to claim 1, wherein the tape forming the slip-sheathcomprises a cellulose fibre in a matrix of water-based resin.
 5. Themethod according to claim 1, wherein the winding is performed fromsingular or multiple supplies of strips of fibre reinforcedthermoplastic, driven through a revolving path about the mandrel.
 6. Themethod according to claim 5, wherein the revolving supplies of fibrereinforced thermoplastic strips are reciprocating in the processdirection.
 7. The method according to claim 5, wherein the revolvingsupplies of fibre reinforced thermoplastic strips are stationary in theprocess direction.
 8. The method according to claim 1, furthercomprising: supplying a solidifying temperature to the wound strips offibre reinforced thermoplastic at a location upstream of the second endof the mandrel.
 9. The method according to claim 8, wherein a heater forconsolidating the fibre reinforced thermoplastic is reciprocating in theprocess direction.
 10. The method according to claim 8, wherein a heaterfor consolidating the fibre reinforced thermoplastic is stationary inthe process direction.
 11. The method according to claim 1, wherein thehomogenous composite pipe of unspecified length is pulled off from thefree end of the mandrel onto a large diameter spool.
 12. The methodaccording to claim 1, further comprising: cleaning the composite pipeinterior from residues of slip-sheath material.
 13. The method accordingto claim 12, wherein the cleaning comprises flooding the homogenouscomposite pipe interior with water, and/or mechanically removingresidues of slip-sheath material from the composite pipe interior. 14.The method according to claim 1, wherein the homogenous composite pipeproduced is a flow-line for transportation of fluids.
 15. The methodaccording to claim 1, wherein the homogenous composite pipe produced isa sub-sea structure for the off-shore industry.
 16. The method accordingto claim 1, wherein the homogenous composite pipe produced is aproduction or injection riser for oil and/or gas and/or water.
 17. Themethod according to claim 1, wherein the homogenous composite pipeproduced is an umbilical pipe.
 18. An assembly for producing ahomogenous composite pipe of unspecified length, the assemblycomprising: a mandrel stationary supported in a first end to extendfreely in a process direction from said first end to a second end; aslip-sheath former configured to form a slip-sheath about the mandrel,said slip-sheath former is arranged to apply a tape materiallongitudinally onto the mandrel surface; a winder mechanism revolvingabout the mandrel downstream of said first end, carrying at least onesupply of thermoplastic material strips; a heater surrounding themandrel upstream of said second end; and a puller arranged downstream ofthe mandrel to be connectable to the slip-sheath.
 19. The assemblyaccording to claim 18, wherein operations of the winder mechanism andheater are synchronized with an incremental operation of the puller. 20.The assembly according to claim 18, wherein operations of the windermechanism and heater are synchronized with a continuous operation of thepuller.
 21. The assembly according to claim 18, wherein the slip-sheathformer comprises at least one rotary supply of tape-shaped slip-sheathmaterial arranged upstream of the winding mechanism for feeding the tapelongitudinally along the mandrel.
 22. The assembly according to claim21, the slip-sheath former comprises a tape guide funnel that controlsthe tape to conform to the shape of the mandrel.
 23. The assemblyaccording to claim 18, wherein the puller comprises a large diameterspool driven for rotation, onto which the composite pipe is wound fromthe mandrel.
 24. The assembly according to claim 18, wherein the secondend of the mandrel is non-supported.
 25. The assembly according to claim18, as used for the production of a flow-line for transportation offluids.
 26. The assembly according to claim 18, as used for theproduction of a sub-sea structure for the off-shore industry.
 27. Theassembly according to claim 18, as used for the production of aproduction or injection riser for oil and/or gas and/or water.
 28. Theassembly according to claim 18, as used for the production of anumbilical pipe in the off-shore industry.